1. Field of the Present Invention
The present invention is in the field of data processing systems and, more particularly, data processing systems that employ resistive touch pads as an input device.
2. History of Related Art
Data processing systems frequently employ touch pads as a means of enabling user input to the system. Touch pads are widely implemented for at least two different applications. In notebook computer applications, touch pads often serve the function of a traditional pointing device such as a computer mouse. In point-of-sale (POS) applications, touch pads are used to facilitate retail transactions by providing a non-paper method for receiving signatures.
In both notebook computer applications and POS applications, designing an optimal touch pad involves a tradeoff between competing considerations. Ideally, touch pads should readily recognize user input while, at the same time, touch pads should be robust enough to reject unintended or incidental inputs, frequently referred to as “palm events” caused when the user, or an article associated with the user, makes unintended contact with the touch pad. Palm events can occur when the user's palm, finger, jewelry, etc., contact the touch pad.
Touch pads are typically designed to balance these competing considerations by targeting the minimum force required for sensors in the touch pad to recognize a particular touch as an intended input. The higher this minimum force is, the more robust the touch pad is to accidental touches, but the less sensitive the touch pad is to intended touches. Conversely, if the minimum force is too low, the touch pad will be quite sensitive to intended touches, but may not be able to adequately reject unintended touches. It would be desirable to implement a touch pad that was, simultaneously, highly sensitive to intended input, and highly robust against palm events and other unintended input.